1. Field of the Invention
The present invention relates to a display device that performs image display by modulating input light with respect to each display dot and outputting the modulated light.
2. Description of the Related Art
As one of the optical modulation devices that modulate light by absorbing light having a particular wavelength, interference filters, such as etalon filter and the like, are put into practical use. The conventional interference filters require a high degree of smoothness and accuracy for the thickness of the film, making them difficult to manufacture and requiring high costs, in particular, those with large display area. In addition, the optical modulation property is fixed due to the rigid structure. Thus, different interference filters are required for different wavelengths to be absorbed (transmitted), which has been an obstacle for flexibly responding to design changes in optical systems.
Under these circumstances, International Patent Publication No. WO2002/082042 discloses an optical modulation device with a porous body having pores (nodes) with a diameter of 1.0 to 1.6 μm in which a fluid is filled. The optical modulation device has a pore diameter which is greater than the wavelength of the input light, forming a photonic crystal structure, and performs optical modulation by the interference effect of the photonic crystal structure.
Japanese Unexamined Patent Publication No. 2001-174719 discloses an optical modulation device with a case having a pair of transparent walls disposed spaced apart in the optical path. The distance between the walls is adjustable, and the case is filled with a fluid. In the optical modulation device, multipath reflection (resonance) occurs between the pair of transparent walls. Consequently, multipath interference occurs, and light having a particular wavelength is absorbed, thereby the light is modulated.
Each of the optical modulation devices described in the aforementioned patent publications may alter the optical modulation property by changing the fluid filled therein, but it is difficult for them to achieve fine and high resolution optical modulation.
Under the circumstances described above, the inventor of the present invention has conducted research work and invented a new optical modulation device which allows fine and high resolution optical modulation with changeable optical modulation property. Further, the device is easy to manufacture, and those with a large display area may be manufactured. The inventor of the present invention has continued the research work and found that the optical modulation device described above is applicable as a new display device in which image display is performed by modulating input light with respect to each display dot and outputting the modulated light. Neither of the patent publications described above mentions the applicability of the device as a display device. What is more, there has been no such idea itself as to applying the optical modulation devices, such as interference filter and the like, to a display device in the past.
As one of the display devices that perform image display by modulating input light with respect to each display dot and outputting the modulated light, a liquid crystal device is known. The liquid crystal device includes a pair of base plates, each with an electrode, disposed opposite to each other with a liquid crystal layer interposed therebetween. In the liquid crystal device, specifically polarized light is inputted to the liquid crystal layer through a polarizer, and the light transmitted through the liquid crystal layer is outputted to the viewer again through the polarizer. Thus, a certain amount of light is absorbed by the polarized, and the light utilization efficiency is degraded by that much. Further, in order to provide full color display using the liquid crystal device, a color filter is required which absorbs a certain amount of light and the light utilization efficiency is degraded by that much.
In contrast, the new display device discovered by the present inventor is capable of performing image display without using any polarizer, and providing full color display without using any color filter. That is, the present invention provides a new and novel display device having higher light utilization efficiency than the conventional liquid crystal device.